‘ And the chiefs (literally ‘corner-tower') of all the people, even of all the tribes of Israel, presented themselves in the assembly of the people of God. Four hundred eleph of footmen that drew sword.'
The leading men (those who were the ‘corner-tower', the strong point) of all the tribes of Israel now gathered together to consider what had happened. This may be a smaller group than Judges 20:1, a gathering of the most important men to hear the case. ‘The assembly' is a word regularly used of Israel in Deuteronomy.
“Four hundred eleph of footmen that drew sword.” The word eleph came to mean a thousand, but prior to that was probably a smaller number representing a clan, a sub-tribe, a family, a fighting unit, or in some cases a captain. This probably represents the number gathered as a whole (those in Judges 20:1) rather than the number of chiefs. There were four hundred units of fighting men, which may suggest roughly four hundred chiefs, ‘leaders of thousands' (Exodus 18:21; Exodus 18:25), each with his supporting unit.
Comparison with Judges 20:17 demonstrates that they excluded Benjaminites. They had not responded to the call. It would seem then that the leaders had gathered together, with supporting fighting men, from all the tribes of Israel, excluding Benjamin. Possibly they were excluded because the trial involved some of their people, and therefore them, but more likely it was because they refused to come.
When considering such numbers in the Old Testament we must always remember, 1). That the meaning of ‘number words' changed over the centuries. 2). That they were not numerically minded and what they wanted to do was convey impressions rather than being concerned with numerical accuracy. 3). That it would be extremely unlikely that anyone would count gatherings even if they could. There were not many specialists in numbering among the tribes. Any assessment would be a very rough approximation, rather aimed at giving an impression than intending to be accurate. On the other hand counting the number of family or military units was a lot easier. 4). That the numbers probably had a significance other than the numerical one. To them numbers conveyed information rather than quantity.